PROJECT 1 ABSTRACT Esophageal cancer comprises two major subtypes, namely esophageal squamous cell carcinoma (ESCC), and esophageal adenocarcinoma (EAC). Esophageal cancer poses grave and pressing clinical problems in the United States and worldwide as reflected by the increasing incidence of EAC in the US, and of the worse prognoses of any cancers as evident in ESCC worldwide. We are focusing on the p120catenin (p120ctn) or CTNND1 and TP53 tumor suppressor genes. Tumor cell progression is illustrated by invasion into the extracellular matrix (ECM) or stoma. This then involves interrelated networks between tumor cells and diverse cell types in the tumor microenvironment. This cross-talk and cross-fertilization trigger a necessary cascade of events prior to dissemination of tumor cells into blood and lymphatic vessels, as well as local and distant metastasis. These include, but are not restricted to, immune cells/inflammatory cells, fibroblasts, endothelial cells, pericytes, neurons, and adipocytes. Our unified view is that p120ctn loss or mislocalization, either of which abrogates its tumor suppressor activities involved in the maintenance of the adherens junctions (complex with E-cadherin) fosters tumor initiation as revealed by our published work on the conditional loss of p120ctn in the mouse esophagus, resulting in invasive ESCC (with local metastasis to lymph nodes) accompanied by desmoplasia and the specific recruitment of myeloid derived suppressor cells (MDSCs) or immature myeloid cells. Tumor progression requires the acquisition of TP53 mutations, which conspire to drive further tumor invasion. The tumor cells interact with cancer-associated fibroblasts (CAFs) and these MDSCs in the tumor microenvironment, involving in part the IL-6 master cytokine that is pro-inflammatory and pro- tumorigenic. Thus, our overarching hypothesis is that p120ctn and TP53 proteins cooperate in tumor progression, TP53 mutation triggers an invasive gene signature that drives tumor cells to invade into the ECM and remodel the ECM, and that tumor invasion in the microenvironment involves the interactions between tumor cells, CAFs and MDSCs. This hypothesis will be pursued by the following interrelated Specific Aims. Aim 1: To evaluate CD38 induction in MDSC populations and its role in immunosuppression via iNOS activation. Aim 2: To elucidate the functional roles of IL-6 as a mediator of cross talk between tumor cells and CAFs in the ESCC microenvironment. Aim 3: To elucidate the functional interplay between p120ctn and TP53 in the esophageal tumor microenvironment. Our successful achievement of these Specific Aims is facilitated greatly by the synergy between the exceptional Projects and the exceptional support provided by the Core Facilities, apart from the broad and deep institutional support.